[GitService::Commit] Fix Commit/CommitDate
[GitService::Commit] Fix Commit/CommitDate

In full_message, which is equivalent to the following `git-log` call:

    $ git log -n1 --pretty=fuller --stat

Has incorrectly defined `Commit` and `CommitDate` since it was added in
commit 49b2146 of `ManageIQ/miq_bot`.

This addresses that, and handles `committer` in the same way that
`author` has been formatted as well.

ManageIQ/miq_bot,ManageIQ/miq_bot,ManageIQ/miq_bot,ManageIQ/miq_bot